1. Filed of the Invention
The present invention relates to a control circuit for a semiconductor laser diode and a method for controlling the same.
2. Related Prior Art
A co-operation agreement for an optical transceiver type of the XENPACK has ruled the maximum current and the rate to increase the power supply current when the transceiver is powered on.
A conventional and general control the supplied current, namely the bias and modulation currents, for the LD comprises an automatic power control (hereafter denoted as APC) operation where an initial parameter is set at the beginning of the powering of the LD and two currents above are adjusted so as to keep the optical output monitored by a photodiode (hereafter denoted as PD) to be equal to the initial parameter. However, the conventional APC operation is unable to follow the maximum current and the power consumption, because the conventional APC operation is unable to suppress the rush current at the powering of the transmitter.
Moreover, when the APC operation begins at the powering of the transmitter, it takes much time to stabilize the optical output from the LD because large overshoots and undershoots in the driving current to the LD inevitably accompany with the APC operation. Thus, the present invention is to provide an optical transmitter that may suppress the rush current at the powering, that is, to adjust the rate of increase of the bias and modulation currents and their practical values at the powering of the transmitter without prolonging the period from the powering to obtain a predetermined optical output from the LD, and is to provide a method to control the rush current of the optical transmitter.